1. Field of the Invention
The present invention relates to an image processing system to which external image input/output devices are to be connected and, more specifically, it relates to input/output control of image data between the system and the external input/output device or between each of the external input/output devices.
2. Description of the Prior Art
Some Image processing systems are connected to a plurality of external image input/output devices. The external devices comprise, for example, an image reader for reading original images, a microscanner for reading images for microfilms, a laser printer for printing out the images, and a laser filmer for forming a microfilm by means of the laser.
Conventionally, when the control of the image bus is carried out from the side of the image processing unit, the bus which is currently used can be known only from the side of the image processing unit. Therefore, if an image reader and a laser printer should be combined so as to be used as a digital copier, the operator can not determine whether this combination is available or not.
An image processing system such as disclosed in U.S. Pat. No. 4,658,299 comprises an image input unit, an image output unit, an image processing unit and an operation unit for instructing the image processing, wherein the image input unit can be activated both from the image input unit and the operation unit. However, when each of the external devices are to be connected in such image processing system to other external image input/output devices, the image bus which is employed for the communication of the image data can be controlled only by the control means controlling the image processing unit. Therefore, the instructions for connecting the input/output devices are applied from the operation unit which instructs the image processing, and the control means controlling the image processing unit controls the image bus which connects the input/output devices according to the instructions from the operation unit, thereby connecting the instructed devices.
However, in this system, the control means in the image processing unit has to monitor external image input/output devices at all times, which is a heavy burden in processing.
Meanwhile, sometimes, the selection of a certain image input device automatically determines an image output device which should be combined with the input device. For example, an image reader and a laser printer should be combined so as to be used as a digital copier, and a microscanner and a laser filmer should be combined so as to be used as a digital filmer. In these cases, it is convenient for an operator to designate from the side of the external image input device the external output device to be combined thereto.